CP scored 98 on the index this year, having earned its place by disclosing high-quality carbon emissions and energy data through CDP's climate change program, CP officials said in a press release. The data is independently assessed against CDP's scoring methodology and marked out of 100. Those organizations graded within the top 10 percent constitute the index.

In 2014, CP was listed on the index with a score of 95.

"CP continues to focus on the most sustainable and efficient operations and it's an honor to again be named as a leader in this area by the CDP," said CP Vice President and Chief Risk Officer Laird Pitz. "We remain steadfast in our belief that transparency and accountability are imperative when it comes to protecting our environment."

At the request of 822 investors who represent $95 trillion in assets, thousands of companies submit annual climate disclosures to CDP. Top scores indicate a high level of transparency in the disclosure of climate change-related information.